A conventional centrifugal slurry pump generally includes an impeller having multiple vanes and which is mounted for rotation within a volute casing. The slurry pump imparts energy to the slurry through the centrifugal force produced by rotation of the impeller. The slurry enters into the impeller through an intake conduit positioned in line with the rotating axis and is accelerated by the impeller, flowing radially outward into the volute casing and subsequently exiting through a discharge conduit. A suction sideliner is positioned a predetermined short distance away from the impeller suction side, the distance being so small as to substantially preclude slurry flow between the impeller and the suction sideliner.
Slurries are two-phase mixtures of solid particles and fluids in which the two phases do not chemically react with each other and can be separated by mechanical means. Slurries are typically characterized as either non-settling or settling in accordance with the size of the solid particles suspended within the fluid. Non-settling slurries include fine particles (less than 50 μm) which form stable homogeneous mixtures. Settling slurries include coarse particles (greater than 50 μm) which form an unstable heterogeneous mixture. Examples of slurries include oil/water; tailings/water; and coke/water slurries. Such slurries can cause abrasion, erosion, and corrosion, resulting in significant wear to pump parts.
Attempts have been made to reduce wear of the pump parts, particularly, the impeller, volute casing, and suction sideliner. A slurry pump operating at low speeds outlasts a faster running pump. Slower running pumps generally have heavier, larger diameter impellers to spread the energy which causes the wear over a larger area. Various modifications related to the configuration, thickness, number, and arrangement of impeller vanes have been described. For example, thicker impeller vanes are capable of handling an abrasive slurry and minimizing wear, but necessitate a reduction in vane number to avoid narrowing the passageways through which the slurry flows.
Pump parts have been formed of various hard metals, elastomeric, or metal-reinforced elastomeric materials to suit the material being pumped. Rubber-lined pumps are often used for pumping non-settling slurries since the resilience of the rubber can absorb and return the energy generated by the impact of the particles to the slurry; however, rubber-lined pumps can be damaged by sharp, large particles or degraded by hydrocarbons. Metal slurry pumps are suitable for pumping abrasive, settling slurries, with 28% chrome iron being the most common material and stainless steel being used for corrosive slurries. The performance of a chrome impeller may be enhanced by laser cladding which deposits an alloy coating to the surfaces of the impeller.
Among all pump parts, the impeller greatly influences the flow patterns of the slurry and the rate of wear. The average lifespan of an impeller is about 1,500 to 2,000 hours, which approximates only half the lifespan of the slurry pump itself. Thus, increasing the lifespan of the impeller would be greatly beneficial in maintaining pump performance and meeting production targets. During manufacture, an impeller is typically cast as one piece, for example, as a high chrome white iron casting. However, chrome white iron (CWI) has only moderately high wear resistance and there is a limited ability to incorporate more wear resisting materials.
Accordingly, there is a need for improved parts such as suction liners and impeller for a centrifugal slurry pump.